Evaluation of ultrasonography and pathology results of incidental thyroid nodules detected on positron emission tomography- computed tomography: Single center results

Aim: We aimed to determine the thyroid pathologies of patients with thyroid incidentalomas detected on 18F-FDG PET-CT, to obtain clinical, imaging, histopathology, and surgical treatment results, and to reveal the relationship between 18F-FDG uptake patterns and Maximum Standard Uptake Values (SUVmax) and diagnostic results. Material and Methods: Data from 1,837 patients who underwent PET-CT for any reason between January 2021 and February 2024 were retrospectively analyzed. Demographic data, ultrasonography (USG), 18F-FDG PET-CT images, and surgical and histopathological data of all patients meeting the inclusion criteria were reviewed. Results: Patients with uptake (n = 71) were evaluated with US, and thyroid nodules were detected in 46 patients (46/1837) (2.5%). Of the 22 nodules that underwent fine needle aspiration biopsy (FNAB), 12 were diagnosed with benign pathology. Among the six nodules that underwent surgery (2 Bethesda V, 3 Bethesda VI, and 1 Bethesda III), three were confirmed as benign, while the other three (13.6%) were diagnosed as malignant (papillary thyroid carcinoma). The malignancy rate in nodules with focal uptake was 16.6% (3/18). No statistically significant difference was observed in the median SUVmax values between benign and malignant nodules (p = 0.164). Conclusion: It is essential to determine the need for diagnostic evaluations, reveal the outcomes of diagnostic interventions, and raise awareness, especially in patients with focal thyroid uptake observed on 18F-FDG PET-CT imaging. When focal uptake is detected on 18F-FDG PET-CT, it is crucial to perform FNAB if the nodule is considered risky on US, regardless of the SUVmax value.